Strabismus affects millions of Americans. While exact numbers are not known, it is estimated that as many as 24 million people are afflicted with this condition. Strabismus is a visual impairment and can be defined as a condition in which the visual axes of the eyes are not parallel and the eyes appear to be looking in different directions. In divergent strabismus, or exotropia, the visual axes diverge. If the visual axes converge, it is called convergent strabismus or esotropia. One of the dangers associated with strabismus is that the brain may come to rely more on one eye than the other and that part of the brain circuitry connected to the less-favored eye fails to develop properly, leading to a condition called amblyopia (blindness) in that eye.
Unfortunately, there are many cases in which vision therapy of any kind will not be effective. A patient whom has suffered a stroke, has permanent nerve damage, has been diagnosed with amblyopia or a host of other conditions will not respond to the invention, or any type of vision therapy.
Severe strabismus may require surgery. The surgery is designed to increase or decrease the tension of the small muscles outside the eye. These muscles are called the extraocular eye muscles. The six extraocular eye muscles move the eye in all directions. When strabismus surgery or vision therapy is needed, and a child is involved, the sooner it is done, the better the chance of the child achieving normal binocular vision.
While the exact cause of strabismus is not entirely understood, we do know that it is more prevalent in some people than others. Many patients that have been diagnosed with strabismus have suffered a serious blow to the head, causing the brain to send false signals to the extraocular muscles which rotate the eye. Further, senior citizens are often diagnosed with strabismus as well as children with autism and cerebral palsy.
By prismatically redirecting the focal point of each eye to one common visual target, strabismus can be therapeutically treated. The invention accomplishes this through the use of very thin, high index prisms. Once the brain is allowed to interpret one image, the invention can be used to slowly reduce the prism strength in one half diopter increments. With time, the patient may reach a point where the use of the Variable Prism Glasses will no longer be necessary, and use of the invention can be discontinued. Thus, the invention offers a non-surgical alternative to the treatment of strabismus.
The invention described herein is directed at providing a solution to the problem of strabismus. Specific conditions within strabismus relate more directly to the direction of displacement. If the eyes have a tendency toward becoming out of alignment, it is known as a phoria, if they are always displaced, it is a tropia. A phoria will occur with fatigue or under the effect of certain medications or alcohol. Horizontal displacement is more common, be it exophoria/tropia (movement out towards the temple), or esophoria/tropia (movement in towards the nose) than vertical displacement (hyperphoria/tropia which is upward movement of one of the eyes). Additionally, please note that hvpophoria/tropia is not described, as hyperphoria/tropia is described for either the right or left eye.
It is important to note that a patient diagnosed with strabismus can be afflicted with more than one type of directional misalignment. The invention treats all types of directional misalignment, whether it is horizontal or vertical, or a combination of the two. Additionally, it will treat convergence insufficiency which is another type of horizontal strabismus occurring when both eyes turn inward when reading. Moreover, the invention treats each eye separately; regardless of the opposite eyes directional displacement. Strabismus can also be called Convergence Insufficiency (CI).
Phoria is a tendency for the eye to become out of alignment when one eye is obstructed; Tropia occurs when the eye is out of alignment even when both eyes are unobstructed.
The novel present invention of variable prism glasses seeks to address these well documented problems experienced by both the medical community and patients. No relevant prior device has been found after extensive searching through databases and trade literature.
The invention may allow the medical community to alleviate the effects of strabismus, and in some cases, eliminate it. There are two methods of treatment available, and are referred to as active (or therapeutic) treatment and passive treatment.
Active treatment provides the health care provider with a varied range of therapeutic options. The health care provider has the ability to change the treatment program as often as necessary without the interruption of ordering new fixed prism glasses, as the invention can be adjusted as often as necessary to meet the ever changing needs of the patient. The objective of active treatment is to therapeutically retrain the eye muscles and brain to realign the eyes to just one visual target.
When the invention is used in a passive fashion, it allows the patient to manipulate the prism strength without removing the invention. Further, the invention allows the patient to adjust the prism power to the minimum strength required. This is a function that is not possible with a standard pair of prism glasses where no variability is possible. It is important to note that passive treatment is not therapeutic treatment; it is not the objective of passive treatment to permanently alleviate or eliminate strabismus. Since it is well known that the eye muscles develop fatigue as the day progresses, the invention, when used passively, simply allows the patient to adjust the amount of prism needed as the day progresses, thereby accurately countering the subjective effects of strabismus.
In view of the visual problems associated with the modern day active and passive treatment of strabismus, the invention addresses these problems and provides a unique solution, often solving visual blurring and diplopia associated with strabismus, through the use of rotating prisms integrated into a standard pair of eyeglasses frames.
Normal binocular vision provides the patient with a clear stereoscopic image of one visual target creating a single clear visual image consisting of both depth and shape. A person afflicted with strabismus (malalignment of both eyes) lacks this ability, as the eyes as a set, lack the ability to fuse on one visual target at the same time. The prism lenses in the present invention rotate to change the visual target, and allow the patient to realign incoming light onto the fovea, producing one visual target, often creating normal fusion of binocular vision for patients treated.
It is important to note that when the invention is used passively, that is, by the patient, the glasses meet the ever-changing prism needs of the patient through minor adjustment. When used actively, therapeutically, the setting of the glasses can be preselected by the health care provider in charge of the patient's visual therapy. It is the intent that the strength of the variable prism would be to reduce the amount of prism, thus reducing or eliminating the patients strabismus and need for the invention altogether.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in, the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. In addition, it is to be understood that the phraseology and terminology employed herein, are for the purpose of description and should not be regarded as limiting.